Composite metal strips



E. w. PALMER ETAL 3,421,866

COMPOSITE METAL STRIPS Filed Jan. 5. 1966 Jan. 14, 1969 EA PE R i I /m EL S mmmm an m ummm N m M W15 0 W HR 1 T nu. mM E M A United StatesPatent 6 Claims This invention relates to composite metal strips andmore particularly it relates to the manufacture of metal strips whichhave elongated wires interlocked within the body of the metal strip. Theinvention consists of .a method and apparatus for manufacturing thesemetal strips and to the composite metal strip per se.

In the fabrication of metal goods, particularly strip metal, theproperties of the strip metal can be improved by forming a compositemetal structure from separate and often very dissimilar metal members.This is particularly true when it is desirable to retain the basic stripform structure and improve its structural or physical properties.

For example, the mechanical strength of a metal strip can be improvedconsiderably by interlocking at least one and preferably a plurality ofelongated laterally spaced wires within the body of the metal stripwithout destroying the basic structure of the metal strip itself. Inthis way a normally softer metal can be reinforced by incorporatingwires made from a metal which might have for example, greater hardnessor spring than the metal strip. For a further example, metal stripswhich have superconducting wires interlocked within the body of a metalstrip which is not superconducting at the temperatures at which thewires are superconductive are particularly useful in many practicalapplications of superconductivity.

The composite metal strip of the invention is comprised of a metal striphaving at least one and advantageously a plurality of elongatedlaterally spaced grooves formed into one broad face of the strip. Awire, having a smaller diameter than the depth of the groove, ispositioned in each groove in flush contact therewith. Integral strip orflap portions partially cut or severed from the metal strip alongopposite sides of the groove adjacent the broad face of the strip areinfolded relative to each other and are clinched about the wire tointerlock the wire to the strip. It has been found that composite metalstrips formed in this way can be characterized as being rein forced inthat they generally have more elastic properties than the metal stripalone and are more resistant to bending along the plane of the metalstrip. Of course the choice of metal wire influences the properties ofthe composite strip. In one useful application the metal wires areformed from a superconducting metal and the metal strip is formed from ametal which has normal conductivity but is not superconducting at thelow temperatures at which the wire is a superconductor. It is preferablein this application that the metal strip have good conductiveproperties, both thermal and electrical, at this low temperature.

In a magnet coil formed of superconducting wire alone, if for any reasonany part of the wire reaches a temperature above the critical pointwhere superconductivity is lost, the resistance introduced causes anabrupt decrease'in the high current flowing in the coil, creating forcesthat may destroy the coil. With the superconductive wire embedded instrip of good electrical and thermal conductivity, however, the wire maybe loaded much more heavilybecause it is eifciently cooled by the strip,

and if a normal spot does occur, it is shunted by a relatively largemass of material of excellent conductivity, avoiding catastrophicchanges in current. In fact, a coil made from the composite strip may bedeliberately overloaded to the point where appreciable resistance isindicated, and brought back to normal fully superconductive operation,without sudden drastic changes in current flow.

The method of forming these composite strips also offers certainadvantages both in its simplicity and in the improved product it forms.The method consists of forming a plurality of elongated laterally spacedgrooves into one broad face of the strip and positioning a wire in eachgroove so that it is in flush contact with the metal strip defining thegrooves. Integral strip portions are separated by partially cutting themaway from opposite sides of the groove adjacent the broad face of thestrip and these integral strip portions are then infolded toward eachother and clinched about the wire to interlock the wire to the strip.This method is also preferably formed in a continuous operation.

While simple in general principle, the method of forming these compositestrips required finding and applying new concepts before successfuloperation was achieved. For example, repeated attempts to roll groovesof the desired configuration into strip of the desired thickness wereunsuccessful; the upper corners of the groove were always rounded off atprecisely the point where a maximum amount of metal was needed forclinching. The idea of over-filling the roll pass, by feeding in stripthicker than desired on the exit side, finally gave satisfactory grooveconfiguration. For grooved strip 0.040 inch thick, the roll should befed with strip thicker than 0.040 inch, up to as much as 0.050 inchthick. Likewise, in clinching the wire, it is essential that noelongation of the strip be permitted to result from this operation, orthe embedded wire may be deformed or unduly stressed. The proportion ofthe cross section displaced in clinching must be carefully related tothe residual cross section to obtain satisfactory results.

The apparatus for performing the method of the in vention consists ofmeans for forming elongated grooves into one broad face of the strip asit is fed therethrough. It further includes wire positioning meanslocated adjacent the groove forming means which serves to position thewire within the groove so that it is in flush contact with the portionof the metal strip. Additionally, means are provided for separating theintegral strip portions on opposite sides of the grooves and infoldingthe strip portions toward each other and clinching them about the wireto interlock the wire to the strip. This apparatus is also preferablyformed to perform the operation on a continuous basis.

A preferred embodiment of the invention is described hereinbelow withreference to the drawing wherein:

FIG. 1 is a side elevation partly in section of apparatus for performingthe method of the invention;

FIG. 2 is an enlarged section taken along the lines 2-2 of FIG. 1;

FIG. 3 is an enlarged section taken along the lines 3-3 of FIG. 1;

FIG. 4 is a greatly enlarged section taken along the lines 44 of FIG. 1;and

FIG. 5 is a fragmentary perspective of the composite metal strip of theinvention.

Referring now to the drawings, apparatus is shown for manufacture of acomposite metal strip which is shown in FIG. 5 consists of a metal strip10 and a plurality of laterally spaced elongated wires 11 which arepositioned within grooves 12 formed in the body of the metal strip. Inorder to understand the small size of the strips which are used in thisapplication it is to be noted that the wire in one application had adiameter of 0.012 inch and the width of the groove was essentially thesame size as the wire. The metal strip had a width of 0.50 inch and the3 thickness of the strip was 0.040 inch with the depth of the groovebeing 0.020 inch. Five such wires were provided and they were spacedapart about 0.087 inch.

In another application the wire and strip sizes were the same as above,but nine wires were embedded with a spacing of about 0.050 inch. Thisrepresents the maximum number of 0.013 inch diameter wires that can beembedded in a 0.500 inch wide strip, since a greater number leavesinsuflicient strip between wires for reliable and proper clinchingaction.

The composite metal strip can be constructed so as to produce acomposite metal structure which increases the strength of the metalstrip. For example piano wire has been used in a relatively soft copperstrip and it has been found that the physical properties of thecomposite strip, particularly in its resistance to bending and itselastic memory upon bending is greatly increased.

It is also intended to use the composite metal strip' constructed asshown and described in superconductor applications. In such anapplication the wires are made from a superconductive material, thechoice of which, from among those that can be fabricated as wire,depends chiefly on the superconductivity characteristics.Niobiumzirconium alloys have been used. Copper and aluminum have beenused successfully as the strip metal; both metals are easily andeconomically formed into metal strips.

As shown in FIG. 1 the strip is continuously fed in a linear path into achamber 13 which is substantially closed with the exception of an inletopening 14 at one end of the chamber and an outlet opening 15 at theopposite end of the chamber through which the strip is allowed to pass.The chamber is shown because in some applications, for example if themetal strip was formed of aluminum, it would be desirable to maintainthe strip within an inert atmosphere while the strip is being worked onin order to prevent oxidation of the strip metal surface within thegrooves prior to confining the wire within the body of the strip. Anyinert gas which will prevent oxidation of the aluminum can be used, oralternatively the chamber could be filled with an oil bath or some otherliquid which will accomplish the same effect.

Positioned within the chamber 13 are a pair of groove forming rollers16. The groove forming rollers consist of a bottom roll 17 which has aflat annular surface 18, as shown in FIG. 2 and flange portions 19 and20 extending along opposite sides of the flat annular surface 18. A top'roll 21 has a width substantially equal to the opening defined betweenthe flange portions 19 and 20 and fits closely therebetween. The toproll 21 has a plurality of laterally spaced annular ribs 22 formedthereabout. The space between the top roll 21 and the flat surface 18 ofthe bottom roll 17 defines a groove forming station.

through which the metal strip is fed and grooves are formed by theannular ribs 22 of the top roll 21. The grooves are formed into onebroad surface of the strip, usually approximately half way into the bodyof the strip and have a depth greater at least than the diameter of thewire which is to be fed into the grooves. The thickness of the grooves,however, should be substantially equal to the diameter of this wire sothat there is flush contact therebetween. Immediately upon emerging fromthe groove forming rolls 16 the strip 10 is fed to a wire feedingstation 24. A supply roll 25 containing as many strands of wire 11 asthere are grooves is stripped from the roll and is passed around a guideroll 27 with the wires being fed into a wire positioning device 28. Thewire positioning device 28 consists of a base member 29, shown in FIG. 3which has upwardly extending flange portions 30 and 31. Secured to theflange portions 30 and 31 is a top plate 33. The top plate has aplurality of laterally spaced finger portions 34 which are of a widthwhich permits them to be inserted into the grooves 11 to wipe the wires12 into the base of the grooves 11. Alternatively, the fingers may bereplaced with narrow wheels serving the same function.

The metal strip 10 with the wires in flush contact with the base andside portions of the metal strip defining the grooves 11 is then fed toa wire interlocking station 26. The interlocking station 26 is comprisedof a bottom roll 37 which is of essentially the same construction as thebottom roll 17 of the groove forming rolls and has a top roll 38 whichfits into the bottom roll 37 in the same manner as the top roll 21 ofthe grooving apparatus. Here, however, a plurality of laterally spacedannular cutting and clinching dies 40 are formed on the top roll 38.These clinching dies consist of a pair of sharp marginal cutting edges41 and 42 which have an angular recess 43 therebetween. The cuttingedges 41 and 42 are defined by surfaces which meet at an angle less thanand preferably at about 60 as shown in FIG. 4, and are spaced about adistance slightly larger than the width of the groove 12. As shown inFIG. 4 when the metal strip 10 with the wire 11 contained inthe groove12 is fed through the clinching rolls 36 the sharp edges 41 and 42 cutthrough and into the board surface of the metal strip. This cuttingforms separate integral strip or flap portions 44 and 45 on oppositesides of the grooves which are displaced by the top roll 38 with theintegral strip portions riding in the recess 43 and are simultaneouslyinfolded toward each other. The edges 47 and 48 of the integral stripportions which once defined the marginal edge of the broad surfaceadjacent the grooves are joined together in substantially abuttingrelationship as the integral strip portions are clinched about the wireto interlock the wire to the strip.

The integral strip portions remain securely and integrally attached tothe strip in the middle of the body of the strip and it is only theportion adjacent the broad face through which the grooves are cut thatis infolded about the wire. By this interlocking, the basic structure ofthe metal strip remains the same in that there is no bending ordistortion of the strip. Only portions of the strip are modified bybeing grooved and portions adjacent the groove are infolded to lock thewire in the strip; but even this grooving and interlocking does notdestroy the basic continuity of the structure, rather it simply permitswires to be interlocked within the strip such that they are embeddedsubstantially midway between the broad faces of the strip.

Although it is not essential that the edges 47 and 48 be in abuttingrelationship, this is desirable in many applications particularly if themetal strip material is aluminum and the inner wall surfaces which arein contact with the wire must be preserved from the formation of anoxidic layer. In this instance it would be desirable to cold weld theedges together to get a true seal. If, however, the metal strip wereformed from copper, which is not susceptible to oxidation, the wirecould be interlocked and clinched within the metal strip withoutabutting these edge portions.

We claim:

1. A composite strip comprising:

(a) ametal strip,

(b) at least one elongated groove formed into one broad face of thestrip,

(0) a wire positioned in the groove in flush contact therewith, saidwire having a smaller diameter than the depth of said groove, and

(d) integral strip portions partially cut from the metal strip alongopposite sides of the groove adjacent the broad face of the stripinfolded relative to each other and clinched about the wire to interlockthe wire to the strip.

2. A composite strip according to claim 1 in which a plurality ofelongated laterally spaced grooves are formed into one broad face of thestrip, and a wire is positioned in each groove in flush contacttherewith.

3. A composite strip according to claim 1 in which the wire is formed ofa superconductive metal and the strip is formed of a metal which hasnormal conductivity at the low temperatures at which the wire is suerconductive. References Cited 4. A con iposite strip according to claim1 in which the UNITED STATES PATENTS metal str1p 1s cop-per.

5. A composite strip according to claim 1 in which the 2,215,477 9/1940Plpkm metal Strip is aluminum 2,688,781 9/1954 Fahlberg et a1 29-191.6

6. A composite strip according to claim 1 in which 5 2945,454 7/ 1960 f29-1915 the integral strip portions cut from the opposite sides of3,153,279 10/1954 Chessln the grooves adjacent the broad face of thestrip and RICHARD DEAN, Primary Examiner. clinched aboutthe wire arefolded down with the edge surface which once defined a portion of thebroad face of the strip substantially abutting each other. 10 29.493,1935

1. A COMPOSITE STRIP COMPRISING: (A) A METAL STRIP, (B) AT LEAST ONEELONGATED GROOVE FORMED INTO ONE BROAD FACE OF THE STRIP, (C) A WIREPOSITIONED IN THE GROOVE IN FLUSH CONTACT THEREWITH, SAID WIRE HAVING ASMALLER DIAMETER THAN THE DEPTH OF SAID GROOVE, AND (D) INTEGRAL STRIPPORTIONS PARTIALLY CUT FROM THE METAL STRIP ALONG OPPOSITE SIDES OF THEGROOVE ADJACENT THE BROAD FACE OF THE STRIP INFOLDED ELATIVE TO EACHOTHER AND CLINCHED ABOUT THE WIRE TO INTERLOCK THE WIRE TO THE STRIP.